Hybrid Materials Doped with Covalently Bound Perylene Dyes through

Nanostructured Hybrid Organic-Inorganic Solids from Molecules to Materials. Bruno Boury , Robert J. P. Corriu. 2009,. Enhanced laser action of Perylen...
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Chem. Mater. 2000, 12, 352-362

Hybrid Materials Doped with Covalently Bound Perylene Dyes through the Sol-Gel Process M. Schneider and K. Mu¨llen* Max-Planck-Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany Received May 6, 1999. Revised Manuscript Received November 10, 1999

We synthesized solubilized alkoxysilane-modified perylene derivatives which were covalently attached to an inorganic host matrix, prepared via the sol-gel process. It was shown that the covalent attachment of the alkoxysilane-modified perylenes led to more homogeneous sols and higher concentrations of the dyes in the sol than the physical admixing of corresponding derivatives. Furthermore, we found that modifying the inorganic network with organic groups caused better solubility characteristics for the perylene derivatives. Attachment of the alkoxysilane-modified perylene derivatives was improved using a more reactive network precursor such as zirconium n-propoxide. Monoliths were prepared by using special temperature programs developed for each sol. Photostability tests of these monoliths showed that chemical attachment of the chromophores led to a significant improvement in the photostability in comparison to their physically admixed analogues.

Introduction The sol-gel process1-3 is a well-known technique for forming inorganic-organic glasslike materials. Using this method, a network-former and a network-modifier can be combined to develop materials with attractive properties, in particular to mechanical, thermal, and chemical stability. In addition alkoxysilane monomers, the alkoxides,4 alcoholates, or halogenides of titanium, zirconium, aluminum, or boron are used as networkforming reagents.5,6 The metalates are first transformed into the corresponding hydroxides by controlled hydrolysis and condensation reactions, catalyzed by acid or base, which result in the inorganic oligomers or polymers upon removal of water.7 The substitution of the alkoxide group at the silane by an alkyl or aryl allows modification of the inorganic network with organic groups.1 In this way composite materials with high transparency can be prepared. Another possibility to establish unprecedented material properties is the incorporation of fillers such as titanium dioxide or aerosils or the doping of the composites with molecules such as fullerenes8 or dyes.9-12 Sol-gel glasses doped with organic chromophores have numer(1) Schmidt, H. Better Ceramics through Chemistry IV. Mater. Res. Soc. Symp. Proc. 1980, 180, 865-870. (2) Jones, R. W. Fundamental principles of the sol-gel-technology; The Institute of Metals, 1989. (3) Schmidt, H. J. Non-Cryst. Solids 1988, 100, 51-54. (4) Brinker, C. J.; Scherer, G. W. J. Non-Cryst. Solids 1985, 70, 301. (5) Schmidt, H.; Kaiser, A. Glastechnische Ber. 1981, 54, 41. (6) Schmidt, H. VDI-Ber. 1989, No. 796, 51. (7) Hench, L. L.; West, J. K. Chem. Rev. 1990, 90, 33-72. (8) Kraus, A.; Schneider, M.; Gu¨gel, A.; Mu¨llen, K. Mater. Chem. 1997, 7 (5), 763. (9) Fujii, T.; Nishikiori, H.; Tamura, T. Chem. Phys. Lett. 1995, 233, 424-429. (10) Avnir, D.; Kaufman, V. R.; Reisfeld, R. J. Non-Cryst. Solids 1985, 74, 395. (11) Avnir, D.; Levy, D.; Reisfeld, R. J. Phys. Chem. 1984, 88, 5956. (12) Makishima, A.; Tani, T. J. Am. Ceram. Soc. 1986, 69 (4), C72C74.

ous applications such as dye-lasers,13 nonlinear optical materials,14 biosensors, or luminescence solar collectors.15 Dyes are normally physically incorporated into the hybrid matrix. With suitable functionalization of the dye molecules they can also be covalently attached to the silica network.16 In the case of the azochromophore disperse red 1, this method leads to higher concentrations and better orientation of the dye molecules in an electric field.17 Dyes derived from perylene,18-20 e.g., perylene-3,4dicarboximides 1 and perylene-3,4:9,10-tetracarboxdiimides 2, as shown in Chart 1, have particularly attractive optical properties. While they are highly fluorescent, their advantage over the azochromophores or the rhodamine dyes is high photostability, which renders them interesting for industrial applications.21 In this paper we present novel perylene derivatives which are covalently bound to different sol-gel matrixes; we further compare the different methods of incorporation of the perylenes into the sol-gel matrix (physical admixing and chemical attachment) with respect to the maximum potential concentration of the dyes and the photostability of the monoliths prepared from the sols. (13) Dunn, B.; Mackenzie, J. D.; Zink, J. I.; Stafsudd, O. M. Proc. SPIE Int. Soc. Opt. Eng. 1990, 1328, 174. (14) Mac Chesney, J. B. Proc. SPIE Int. Soc. Opt. Eng. 1989, 988, 131. (15) Reisfeld, R.; Jorgensen, C. K. Struct. Bonding 1982, 49, 1. (16) Chambers, R. C.; Haruvy, Y.; Fox, M. A. Chem. Mater. 1994, 6, 1351-1357. (17) Riehl, D.; Chaput, F.; Levy, Y.; Boilot, J.-P.; Kajzar, F.; Choilet, P.-A. Chem. Phys. Lett. 1995, 245, 36-40. (18) Feiler, L.; Langhals, H.; Palborn, K. Liebigs Ann. 1995, 12291244. (19) Rademacher, A.; Ma¨rkle, S.; Langhals, H. Chem. Ber. 1982, 115, 2927-2934. (20) Quante, H.; Geerts, Y.; Mu¨llen, K. Chem. Mater. 1997, 9, 495500. (21) Zollinger, H. Color Chemistry; Verlag Chemie: Weinheim, 1987.

10.1021/cm9910613 CCC: $19.00 © 2000 American Chemical Society Published on Web 02/04/2000

Hybrid Materials Doped with Perylene Dyes Chart 1. Perylene Derivatives: Perylene-3,4-dicarboximides 1 and Perylene-3,4:9,10-tetracarboxdiimides 2

Experimental Section Instrumental Methods. 1H and 13C NMR Spectroscopy: Bruker AC 300 MHz and Bruker AMX 500. 29Si NMR spectroscopy: Bruker AMX 500. Mass spectrometry, field desorption (FD): Finnigan MAT 312. Infrared spectroscopy: Nicolet FT-IR 320. UV-vis absorption spectroscopy: PerkinElmer Lambda 9. Melting points (uncorrected): Bu¨chi melting point apparatus. Elemental analyses were performed at the Department of Chemistry and Pharmacy of the University of Mainz. Photostability tests were carried out at BASF AG: xenotest 450 with a lightening power of 810 W/m2 ( 300 °C. 1H NMR (500 MHz, CDCl3, 25 °C): δ (ppm) ) 8.34 (d, 3J(H,H) ) 8.23 Hz, 2H, Ar-H); 8.19 (d, 3J(H,H) ) 7.69 Hz, 2H, Ar-H); 8.12 (d, 3J(H,H) ) 8.24 Hz, 2H, Ar-H); 7.79 (d, 3J(H,H) ) 8.24 Hz, 2H, Ar-H); 7.50 (t, 3J(H,H) ) 7.69 Hz, 2H, H8,11); 4.13 (t, 3J(H,H) ) 8.23 Hz, 2H, N-CH2); 3.82 (q, 3J(H,H) ) 7.31 Hz, 6H, OCH2); 1.82 (m, 2H, N-CH2-CH2), 1.21 (t, 3J(H,H) ) 7.13 Hz, 9H, OCH2CH3); 0.78-0.75 (m, 2H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ (ppm) ) 163.71 (CdO); 136.75; 134.13; 131.15; 130.72; 129.47; 128.96; 127.63; 126.88; 126.42; 123.43; 120.73; 119.90; 58.42 (OCH2); 42.87 (N-CH2); 29.13 (N-CH2-CH2); 18.31 (OCH2CH3); 8.10 (Si-CH2). FD-MS: m/z (u e0-1) found 525.6 (100, M+), calcd 525.67. IR (KBr): 1693 (νCdO); 1638 (νCdO); 1104 (νC-O); 1079 (νSi-O-C) cm-1; UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 264 (28 579); 319 (4934); 331 (4339); 485 (32 421); 507 (30 177). Anal. Calcd for C31H31NO5Si: C, 70.83; H, 5.94; N, 2.66. Found: C, 57.84; H, 6.34; N, 4.61 (the differences (22) Standard method of the International Standard Organization (ISO): H. Zollinger, Color Chemistry, 2nd ed., VCH: New York, 1991. (23) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals, 2nd ed.; Pergamon Press: Frankfurt, 1987.

Chem. Mater., Vol. 12, No. 2, 2000 353 between the found and calculated values of the elemental analysis will be discussed in the Results and Discussion section). N-(3-Trimethoxysilyl)propylperylene-3,4-dicarboxmonoimide (“Dimer”) (6). A 644 mg (2 mmol) sample of perylenedicarboxylic monoanhydride (4), 100 mL of dry methanol, and 1.432 g (0.008 mol) of (3-aminopropyl)trimethoxysilane (APTMS) (7) were refluxed under an argon atmosphere for 24 h. After suction filtration the obtained powder was washed with cold methanol. The product was isolated in 86% yield. Mp > 300 °C. 1H NMR (500 MHz, CD2Cl2, 25 °C): δ (ppm) ) 8.33 (d, 3J(H,H) ) 8.25 Hz, 2H, Ar-H); 8.20 (d, 3J(H,H) ) 7.72 Hz, 2H, Ar-H); 8.11 (d, 3J(H,H) ) 8.23 Hz, 2H, Ar-H); 7.78 (d, 3J(H,H) ) 8.24 Hz, 2H, Ar-H); 7.50 (t, 3J(H,H) ) 7.74 Hz, 2H, H 3 8,11); 4.12 (t, J(H,H) ) 8.20 Hz, 2H, N-CH2); 3.48 (s, 6H, OCH3); 1.81 (m, 2H, N-CH2-CH2); 0.76 (m, 2H, Si-CH2). 29Si NMR solid CP-MAS: δ (ppm) ) -48 (T1). FD-MS: m/z (u e0-1) found 920.3 (100, M+), calcd 920.26. IR (KBr): 1689 (νCdO); 1643 (νCdO); 1108 (νC-O); 1075 (νSi-O-C); 1038 w (νSi-O-Si) cm-1; UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 267 (8092); 319 (5971); 379 (1607); 489 (27 975); 514 (25 856). Anal. Calcd for C54H44N2O9Si2: C, 70.41; H, 4.81; N, 3.04. Found: C, 69.90; H, 4.76; N, 3.07. N,N′-Bis(3-triethoxysilylpropyl)-perylene-3,4:9,10-tetracarboxdiimide (8). A 0.785 g (2 mmol) sample of 3,4:9,10-perylenetetracarboxylic bisanhydride (9) (BASF) (purified by repeatedly being dissolved in potassium hydroxide solution and reprecipitated with HCl) was added to a 250 mL Schlenk flask, followed by 70 mL of dry ethanol. The flask was repeatedly evacuated and flushed with argon. After the mixture was stirred for 1/2 h under an argon atmosphere, it was heated in an oil bath to 110 °C. A 3.542 g (16 mmol) sample of (3-aminopropyl)triethoxysilane (APTES) (5) was added dropwise through a septum. The reaction mixture was stirred for 6 h under reflux and under an inert atmosphere. After the mixture was cooled to room temperature, the precipitate was collected by suction filtration and washed thoroughly with cold ethanol. The dark red product was obtained in 82% yield. Mp > 300 °C. 1H NMR (500 MHz, CD2Cl2, 25 °C): δ (ppm) ) 8.60 (d, 3J(H,H) ) 7.93 Hz, 4H, Ar-H); 8.53 (d, 3J(H,H) ) 7.93 Hz, 4H, Ar-H); 4.14 (t, 3J(H,H) ) 7.33 Hz, 4H, N-CH2); 3.78 (q, 3J(H,H) ) 6.71 Hz, 12H, OCH2); 1.84 (m, 4H, N-CH2-CH2), 1.18 (t, 3J(H,H) ) 7.32 Hz, 18H, OCH2CH3); 0.70 (m, 4H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ (ppm) ) 164.44 (CdO); 135.70; 132.59; 130.33; 127.42; 124.35; 124.25; 59.57 (OCH2); 42.75 (N-CH2); 22.70 (N-CH2-CH2); 19.55 (OCH2CH3); 9.29 (Si-CH2). FDMS: m/z (u e0-1) found 798.0 (100, M+), calcd 798.30. IR (KBr): 1693 (νCdO), 1655 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 260 (47 507); 458 (14 267); 489 (36 089); 525 (57 007). Anal. Calcd for C42H50N2O10Si2: C, 63.13; H, 6.31; N, 3.51. Found: C, 58.81; H, 6.18; N, 3.78. N,N′-Bis(3-triethoxysilylpropyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetra-carboxdiimide (10). The mixture of 0.1 g (0.131 mmol) of 1,6,7,12-tetraphenoxyperylene3,4:9,10-tetracarboxylic bisanhydride (11)24 and 0.1745 g (0.789 mmol) of (3-aminopropyl)triethoxysilane (5) in 30 mL of dry ethanol was reacted under reflux and an inert atmosphere for 4.5 h. After suction filtration and washing of the obtained powder with cold ethanol, the product was isolated in 72% yield. Mp > 300 °C. 1H NMR (500 MHz, CDCl3, 25 °C) δ (ppm) ) 8.26 (s, 4H, H2); 7.27 (m, 4H, H4′); 7.13 (m, 3J(H,H) ) 7.69 Hz, 4H, H3′); 6.96 (d, 3J(H,H) ) 7.14 Hz, 4H, H2′); 4.12 (t, 3J(H,H) ) 7.68 Hz, 4H, N-CH ); 3.82 (q, 3J(H,H) ) 7.13 Hz, 2 12H, OCH2); 1.84-1.78 (m, 4H, N-CH2-CH2), 1.21 (t, 3J(H,H) ) 7.14 Hz, 18H, OCH2CH3); 0.71 (m, 4H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ (ppm) ) 163.18 (CdO); 155.80 (C1); 155.38 (C1′); 132.82; 129.94; 124.53; 122.73; 120.51; 120.06; 119.94; 119.63; 58.38 (OCH2); 43.04 (N-CH2); 21.51 (N-CH2-CH2); 18.26 (OCH2CH3); 8.01 (Si-CH2). 29Si NMR (99.38 MHz, CCCl3, 30 °C): δ (ppm) ) -45.8 (T00). FD-MS: m/z (u e0-1) found 1166.9 (100, M+), calcd 1166.41. IR (KBr): (24) Quante, H. Ph.D. Thesis, University of Mainz, 1994.

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Chem. Mater., Vol. 12, No. 2, 2000

1699 (νCdO), 1660 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 286 (44 261); 444 (14 218); 539 (26 015); 576 (33 797). Anal. Calcd for C66H66N2O14Si2: C, 67.90; H, 5.70; N, 2.40. Found: C, 68.36; H, 5.83; N, 2.76. N,N′-Bis(3-triethoxysilylpropyl)-1,6,7,12-tetrakis(4′hexyloxyphenoxy)perylene-3,4:9,10-tetracarboxdiimide (12). The mixture of 58 mg (0.05 mmol) of 1,6,7,12tetrakis(4′-hexyloxyphenoxy))perylene-3,4:9,10-tetracarboxylic bisanhydride (13)24 and 88.5 mg (0.4 mmol) of (3aminopropyl)triethoxysilane (5) in 20 mL of dry ethanol was reacted under reflux and an inert atmosphere for 4.0 h. After suction filtration and washing of the obtained powder with cold ethanol, the product was isolated in 68% yield. Mp > 300 °C. 1 H NMR (500 MHz, CDCl3, 25 °C): δ (ppm) ) 8.07 (s, 4H, H2); 6.88 (d, 3J(H,H) ) 8.79 Hz, 8H, H3′); 6.79 (d, 3J(H,H) ) 8.74 Hz, 8H, H2′); 4.06 (t, 3J(H,H) ) 7.68 Hz, 4H, N-CH2); 3.91 (t, 3J(H,H) ) 6.59 Hz, 8H, Ar-OCH ); 3.75 (q, 3J(H,H) ) 7.14 2 Hz, 12H, OCH2); 1.76 (m, 12H, N-CH2-CH2, Ar-OCH2-CH2); 1.45 (m, 8H, CH2); 1.34 (m, 16 H, (CH2)2); 1.16 (t, 3J(H,H) ) 6.59 Hz, 18H, OCH2CH3); 0.90 (m, 12H, CH3); 0.66 (m, 4H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ (ppm) ) 163.34 (CdO); 156.62 (C4′); 156.21 (C1); 148.44 (C1′);132.80; 122.42; 121.39; 119.85; 119.10; 118.97; 115.96; 77.0 (Ar-O-CH2); 58.37 (OCH2); 43.03 (N-CH2); 31.60 (β-CH2) 29.27 (γ-CH2); 25.74 (CH2); 22.62 (CH2); 21.51 (N-CH2-CH2); 18.26 (OCH2CH3); 14.04 (CH3); 7.99 (Si-CH2). FD-MS: m/z (u e0-1) found 1567.7 (100, M+), calcd 1566.76. IR (KBr): 1698 (νCdO), 1661 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 282 (52 148); 462 (6749); 550 (12 311); 591 (17 666). N,N′-Bis(3-triethoxysilylpropyl)-1,7-diphenoxyperylene3,4,9:10-tetracarboxdiimide (14). The mixture of 100 mg (0.173 mmol) of 1,7-diphenoxyperylene-3,4:9,10-tetracarboxylic bisanhydride (15)24 and 153.6 mg (0.694 mmol) of (3-aminopropyl)triethoxysilane (5) in 20 mL of dry ethanol was reacted under reflux and an inert atmosphere for 3.5 h. After suction filtration and washing of the obtained powder with cold ethanol, the product was isolated in 55% yield. Mp > 300 °C. 1H NMR (300 MHz, CDCl , 25 °C): δ (ppm) ) 9.58 (d, 3J ) 3 8.24 Hz, 2H, H6,12); 8.65 (d, 3J(H,H) ) 8.53 Hz, 2H, H5,11); 8.31 (s, 2 H, H2,8); 7.46 (m, 4 H, Ar-H); 7.29 (m, 2H, H4′); 7.16 (m, 3J ) 7.93 Hz, 4 H, Ar-H); 4.09 (m, 4H, N-CH2); 3.80 (q, 3J(H,H) ) 6.72, 12H, OCH2); 1.84 (m, 4H, N-CH2-CH2); 1.20 (t, 3J(H,H) ) 7.30 Hz, 18H, OCH2CH3); 0.73 (m, 4H, SiCH2). 13C NMR (75 MHz, CDCl3, 25 °C): δ (ppm) ) 163.12 (CdO); 162.71 (CdO); 155.06; 154.84; 130.44; 130.14; 128.71; 127.67; 125.00; 124.89; 124.20; 124.03; 123.03; 122.22; 119.33; 119.21; 58.40 (OCH2); 43.06 (N-CH2); 21.51 (N-CH2-CH2); 18.26 (OCH2CH3); 7.99 (Si-CH2). FD-MS: m/z (u e0-1) found 983.2 (100, M+), calcd 983.23. IR (KBr): 1699 (νCdO), 1662 (νCdO) cm-1; UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 265 (44 391), 393 (9337), 406 (9216), 505 (42 504), 532 (48 605). Anal. Calcd for C54H58N2O12Si2: C, 65.97; H, 5.95; N, 2.85. Found: C, 64.50; H, 5.72; N, 3.50. N,N′-Bis(3-triethoxysilylpropyl)-1,7-bis(4′-tert-butylphenoxy)perylene-3,4:9,10-tetracarboxdiimide (16). The mixture of 50 mg (0.0726 mmol) of 1,7-bis(4′-hexyloxyphenoxy)perylene-3,4:9,10-tetracarboxylic bisanhydride (17)24 and 128 mg (0,578 mmol) of (3-aminopropyl)triethoxysilane (5) in 20 mL of dry ethanol was reacted under reflux and an inert atmosphere for 3.5 h. After suction filtration and washing of the obtained powder with cold ethanol, the product was isolated in 52% yield. Mp > 300 °C. 1H NMR (300 MHz, CDCl3, 25 °C): δ (ppm) ) 9.57 (d, 3J(H,H) ) 8.39 Hz, 2H, H6,12); 8.55 (d, 3J(H,H) ) 8.39 Hz, 2H, H5,11); 8.30 (s, 2 H, H2,8); 7.41-7.38 (m, 4H, H3′); 7.05-7.02 (m, 4H, H2′); 4.08 (t, 4H, N-CH2); 3.74 (q, 3J(H,H) ) 7.25 Hz, 12H, OCH2); 1.79 (m, 4H, N-CH2-CH2); 1.36 (s, 18H, (CH3)3); 1.13 (t, 3J(H,H) ) 6.87 Hz, 18H, OCH2CH3); 0.69 (m, 4H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ (ppm) ) 163.31 (CdO); 162.96 (CdO); 155.40 152.76; 148.12; 130.14; 129.42; 128.91; 128.80; 127.38; 124.34; 124.09; 124.01; 123.91; 122.33; 118.95; 58.35 (OCH2); 43.01 (N-CH2); 34.49 (C(CH3)3); 31.40 (C(CH3)3); 21.53 (NCH2-CH2); 18.18 (OCH2CH3); 8.11 (Si-CH2). FD-MS: m/z (u e0-1) found 1094.0 (100, M+), calcd 1094.47. IR (KBr): 1698 (νCdO), 1659 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 cm-1))

Schneider and Mu¨ llen ) 295 (5310), 433 (8246); 539 (27 944), 574 (36 210). Anal. Calcd for C62H74N2O12Si2: C, 67.98; H, 6.81; N, 2.56. Found: C, 67.58; H, 6.16; N, 2.75. N,N′-Bis(3-triethoxysilylpropyl)-1,6,7,12-tetrakis[4′(1′′,1′′,3′′,3′′-tetramethylbutyl)phenoxy]perylene-3,4:9,10tetracarboxdiimide (18). A 200 mg (0.165 mmol) sample of 1,6,7,12-tetrakis(4′-(1′′,1′′,3′′,3′′-tetramethylbutyl)phenoxy)perylene-3,4:9,10-tetracarboxylic bisanhydride (19)24 was added to a 50 mL Schlenk flask, followed by 20 mL of dry ethanol. The flask was repeatedly evacuated and flushed with argon. After the reaction mixture was stirred for 0.5 h under an argon atmosphere, it was heated in an oil bath to 100 °C. A 73.2 mg (0.32 mmol) sample of (3-aminopropyl)triethoxysilane (5) was added through a septum. The reaction mixture was stirred for 2 h under an inert atmosphere, while the color changed from orange to dark red. The solvent was immediately evaporated under a vacuum and the remaining powder rapidly washed with ice-cold ethanol. The dark red product was isolated in 85% yield. Mp > 300 °C. 1H NMR (500 MHz, CDCl3, 25 °C): δ (ppm) ) 8.10 (s, 4H, H2); 7.25 (d, 3J(H,H) ) 8.54 Hz, 8H, H3′); 6.84 (d, 3J(H,H) ) 8.54 Hz, 8H, H2′); 4.06 (t, 3J(H,H) ) 7.33 Hz, 4H, N-CH2); 3.76 (q, 3J(H,H) ) 6.71 Hz, 12H, OCH2); 1.77 (m, 4H, N-CH2-CH2); 1.71 (s, 8H, CH2); 1.34 (s, 24H, (CH3)2); 1.16 (t, 3J(H,H) ) 7.32 Hz, 18H, OCH2CH3); 0.76 (s, 36H, (CH3)3); 0.66 (m,3J(H,H) ) 8.55 Hz, 4H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ (ppm) ) 163.27 (CdO); 156.17 (C1); 152.70 (C1′); 146.62 (C4′);132.71; 127.67; 122.54; 120.11; 119.56; 119.27; 119.02; 58.36 (OCH2); 57.11 (C(CH3)2) 42.98 (N-CH2); 38.35 (C(CH3)3); 32.42 (C(CH3)2); 31.82 (C(CH3)3); 31.52 (CH2); 21.49 (N-CH2-CH2); 18.25 (OCH2CH3); 7.99 (Si-CH2). 29Si NMR (99.38 MHz, CDCl3, 30 °C): δ (ppm) ) -45.82 (T00). FD-MS: m/z (u e0-1) found 1615.6 (100, M+), calcd 1614.91; IR (KBr): 1700 (νCdO), 1664 (νCdO) cm-1; UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 268 (43 739); 287 (55 546); 449 (17 815); 548 (32 596); 585 (42 347). Anal. Calcd for C98H130N2O14Si2: C, 72.83; H, 8.11; N, 1.73. Found: C, 69.00; H, 8.56; N, 2.70. N-(3-Triethoxysilylpropyl)carbamide Acid 6-(3′-Hexylperylene-9′(10′)-yl)hexyl Ester (20). A 0.8 g (1.83 mmol) sample of 3-hexyl-9(10)-(6′-hydroxyhexyl)perylene (21)25 was added to a 100 mL Schlenk flask, followed by 60 mL of dry tetrahydrofuran. The flask was repeatedly evacuated and flushed with argon. A 0.906 g (3.664 mmol) sample of (3isocyanatopropyl)triethoxysilane (IPTES) (22) was added under an argon atmosphere. The reaction mixture was heated in an oil bath to 60 °C and stirred for 16 h. The solvent was evaporated, and the remaining powder was washed with icecold methanol. It was again dissolved in THF and slowly reprecipitated by addition of methanol/pentane (1:1). The orange product was obtained in 38% yield. For absolute purification a separation by GPC with THF as solvent was possible. However, with this method, the yield was drastically reduced. Mp 100.93 °C. 1H NMR (500 MHz, CDCl3, 25 °C): δ (ppm) ) 8.23-8.19 (m, 3J(H,H) ) 7.68 Hz, 2H, H6,12); 8.128.10 (m, 3J(H,H) ) 7.13 Hz, 2H, H1,7); 7.88 (m, 3J(H,H) ) 8.24 Hz, 2H, H5,11); 7.53 (m, 3J(H,H) ) 7.68 Hz, 2H, H4,10); 7.34 (m, 2H, H2,8); 4.87 (s, 1H, N-H); 4.07 (t, 2H, CO-O-CH2); 3.82 (q, 3J(H,H) ) 7.14 and 6.59 Hz, 6H, OCH2); 3.17 (m, 2H, N-CH2); 3.03 (t, 3J ) 8.24 Hz, 4H, Ar-CH2); 1.81-1.75 (m, 4H, CH2); 1.65 (m, 6H, CH2); 1.49 (m, 4H, CH2); 1.37 (m, 4H, CH2); 1.23 (t, 3J(H,H) ) 7.14 Hz, 9H, OCH2CH3); 0.93 (t, 3J ) 7.13 Hz, 3H, CH3); 0.64 (m, 3J ) 7.68 Hz, 2H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ (ppm) ) 156.69 (CdO); 138.17; 132.99; 132.04; 129.73; 128.84; 127.34; 126.90; 126.78; 126.18; 125.62; 123.63; 123.09; 120.61; 119.97; 119.55; 64.70 (CH2-O-CO); 58.43 (OCH2CH3); 43.09 (N-CH2); 33.24 (Ar-CH2); 31.76; 30.44; 29.91; 29.51; 28.78; 28.01; 25.83 (NCH2-CH2); 22.65; 18.69 (OCH2CH3); 13.61 (CH3); 7.65 (SiCH2). 29Si NMR (99.38 MHz, CDCl3, 30 °C): δ (ppm) ) -45.54 (T00). FD-MS: m/z (u e0-1) found 683.4 (100, M+), calcd 683.40; IR (KBr): 1688 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 (25) Schlichting, P.; Rohr, U.; Mu¨llen, K. Liebigs Ann./Recl. 1997, 395-407.

Hybrid Materials Doped with Perylene Dyes cm-1)) ) 257 (31 307); 401 (11 118); 424 (23 196); 452 (28 808). Anal. Calcd for C42H57NO5Si: C, 73.75; H, 8.40; N, 2.05. Found: C, 73.78; H, 8.55; N, 2.16. 3,9(10)-Perylenedicarboxylic Acid Di[5′-yl-N-(3-triethoxysilylpropyl)]pentyl Ester (23). A 54 mg (0.1 mmol) sample of 3,9(10)-perylenedicarboxylic acid di[5′-hydroxy]pentyl ester (24),26 dissolved in 20 mL of dry pyridine, was added to a 50 mL Schlenk flask. After repeated evacuation and flushing of the flask with argon, 148 mg (0.6 mmol) of (3-isocyanatopropyl)triethoxysilane (22) was added. The mixture was stirred at 80 °C for 4 h, after which the solvent was evaporated. The residue was stirred in methylene chloride under an inert atmosphere for 1 h. The undissolved particles (oligomers of the product) were separated by filtration. The solvent was evaporated and the orange product obtained in 34% yield. Mp > 300 °C. 1H NMR (300 MHz, CDCl3, 25 °C): δ (ppm) ) 8.89 (m, 2H, Ar-H); 8.80 (m, 2H, Ar-H); 8.278.20 (m, 2H, Ar-H); 8.16-8.14 (m, 2H, Ar-H); 7.60 (m, 2H, Ar-H); 4.64 (s, 2H, N-H); 4.36 (m, 4H, Ar-CO-O-CH2); 4.00 (m, 2H, N-CO-O-CH2); 3.75 (q, 3J(H,H) ) 7.26, 6.86 Hz, 12H, OCH2); 3.11 (m, 4H, N-CH2); 1.98 (m, 4H, CH2); 1.78 (m, 8H, CH2); 1.55-1.43 (m, 8H, CH2); 1.20 (t, 18H, OCH2CH3); 0.76 (m, 4H, Si-CH2). FD-MS: m/z (u e0-1) found 1034.3 (100, M+), calcd 1034.49. IR (KBr): 1709 (νCdO), 1637 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 348 (2026); 439 (24 230); 465 (28 947). Anal. Calcd for C52H74N2O14Si2: C, 62.64; H, 7.59; N, 2.71. Found: C, 54.86; H, 6.02; N, 6.78. Bis-N-(3-triethoxysilylpropyl)carbamideAcid6-[Perylene3,9(10)-diyl]hexyl Ester (25). A 125 mg (0.276 mmol) sample of bis-3,9(10)-(6′-hydroxyhexyl)perylene (26)25 was added to a 50 mL Schlenk flask, followed by 25 mL of dry THF. After repeated evacuation and flushing of the flask with argon, 417 mg (1.69 mmol) of (3-isocyanatopropyl)triethoxysilane (22) was added. The mixture was stirred at 60 °C for 1 day under argon. Another 209 mg (0.845 mmol) sample of (3-isocyanatopropyl)triethoxysilane (22) was added, and the mixture was again stirred for 1 day at 60 °C. After the mixture was cooled to room temperature, the solvent was evaporated. The obtained solid was dissolved in 60 mL of dry methylene chloride and stirred for 1 h. The undissolved particles were removed by filtration. The solvent was evaporated and the powder washed with cold methanol. The yellow product was obtained in 68% yield. Mp > 300 °C. 1H NMR (300 MHz, CDCl3, 25 °C): δ (ppm) ) 8.208.15 (m, 2H, H6,12); 8.11-8.06 (m, 2H, H1,7); 7.85-7.81 (m, 2H, H5,11); 7.51-7.45 (m, 2H, H4,10); 7.32-7.29 (m, 2H, H2,8); 4.85 (s, 2H, N-H); 4.05-4.01 (m, 4H, CO-O-CH2); 3.80 (q, 3J(H,H) ) 7.18 and 6.88 Hz, 12H, OCH2); 3.15-3.13 (m, 4H, N-CH2); 2.99 (t, 3J ) 7.97 Hz, 4H, Ar-CH2); 1.75-1.72 (m, 4H, CH2); 1.59-1.56 (m, 8H, CH2); 1.43-1.40 (m, 8H, CH2); 1.19 (t, 3J(H,H) ) 7.14 Hz, 18H, OCH2CH3); 0.63-0.57 (m, 4H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ (ppm) ) 156.40 (CdO); 137.82; 132.58; 131.64; 129.31; 128.46; 126.40; 126.34; 125.83; 119.60; 119.15; 64.64 (CH2-O-CO); 58.04 (OCH2CH3); 43.07 (N-CH2); 32.85 (Ar-CH2); 30.05; 29.05; 28.67; 25.44 (NCH2-CH2); 22.94; 17.85 (OCH2CH3); 7.25 (Si-CH2). FD-MS: m/z (u e0-1) found 946.7 (100, M+), calcd 946.52; IR (KBr): 1690 (νCdO), 1635 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 259 (36 357); 404 (12 911); 427 (26 938); 456 (33 455). Anal. Calcd for C52H78N2O10Si2: C, 65.93; H, 8.30; N, 2.96. Found: C, 62.09; H, 7.72; N, 4.69. Bis-N-(3-Triethoxysilylpropyl)carbamideAcid5-[Perylene3,9(10)-diyl]pentyl Ester (27). The reaction was performed as described for perylene derivative 25. Reaction of 42.46 mg (0.1 mmol) of bis-3,9(10)-(6′-hydroxypentyl)perylene (28)25 and 148.42 mg (0.6 mmol) (second addition, 74.21 mg (0.3 mmol)) of (3-isocyanatopropyl)triethoxysilane (22) in 15 mL of dry THF afforded the yellow product in 72% yield. Mp > 300 °C. 1H NMR (300 MHz, CDCl , 25 °C): δ (ppm) ) 8.15-8.10 (m, 3 2H, H6,12); 8.06-8.01 (m, 2H, H1,7); 7.80-7.75 (m, 2H, H5,11); 7.47-7.44 (m, 2H, H4,10); 7.27-7.24 (m, 2H, H2,8); 4.89 (s, 2H, N-H); 4.01 (m, 4H, CO-O-CH2); 3.81-3.70 (q, 3J(H,H) ) 6.87 u. 7.25 Hz, 12H, OCH ); 3.11 (m, 4H, N-CH ); 2 2 (26) Mu¨ller, G. Ph.D. Thesis, University of Mainz, 1997.

Chem. Mater., Vol. 12, No. 2, 2000 355 2.95 (t, 3J ) 7.63 Hz, 4H, Ar-CH2); 1.75-1.67 (m, 4H, CH2); 1.62-1.52 (m, 8H, CH2, N-CH2-CH2); 1.49-1.44 (m, 4H, CH2); 1.15 (t, 3J(H,H) ) 7.25 Hz, 18H, OCH2CH3); 0.58-0.53 (m, 4H, Si-CH2). 13C NMR (125 MHz, CDCl3, 25 °C): δ ppm) ) 156.78 (CdO); 138.44; 138.04; 132.96; 132.05; 129.76; 128.87; 126.84; 126.35; 126.29; 123.64; 123.27; 120.04; 119.61; 64.72 (CH2-O-CO); 58.45 (OCH2CH3); 43.38 (N-CH2); 33.24 (ArCH2);30.23;29.04;26.13(N-CH2-CH2);23.34;18.43(OCH2CH3); 7.66 (Si-CH2). FD-MS: m/z (u e0-1) found 918.2 (100, M+), calcd 918.48. IR (KBr): 3347 (N-H), 1694 (νCdO), 1643 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 259 (32 724); 404 (11 621); 427 (24 246); 456 (30 112). Anal. Calcd for C50H74N2O10Si2: C, 65.33; H, 8.11; N, 3.05. Found: C, 62.63; H, 7.55; N, 5.56. 6,6′-Di[3,9(10)-perylenediyl]hexanoic Acid Di(3-triethoxysilyl)propylamide (29). (a) A 0.240 g (0.5 mmol) sample of 3,9(10)-bis(5′-carboxypentyl)perylene (30)25 was added to a 100 mL Schlenk flask, followed by 40 mL of dry toluene and 10 mL of dry dimethylformamide. The flask was repeatedly evacuated and flushed with argon. The mixture was heated to 80 °C under argon and stirred until all starting material was dissolved, after which 0.494 g (2 mmol) of (3isocyanatopropyl)triethoxysilane (22) was added through a septum. The reaction mixture was stirred under reflux for 16 h. The solvent was evaporated and the residue thoroughly washed with cold ethanol several times. The powder was dissolved in dry THF and reprecipitated by slow addition of pentane. The product was collected by vacuum filtration in 54% yield. (b) A 0.100 g (0.208 mmol) sample of 3,9(10)-bis(5′-carboxypentyl)perylene (30) was added to a 100 mL Schlenk flask, followed by 50 mL of dry THF. The flask was repeatedly evacuated and flushed with argon. A 0.264 g (2.08 mmol) sample of oxalyl chloride was slowly added at room temperature. The mixture was stirred under reflux for 6 h. The solvent and excess oxalyl chloride were evaporated. A 50 mL portion of dry THF and 2 mL of dry pyridine were added to the resulting acyl chloride-modified perylene 31, followed by 0.046 g (0.208 mmol) of freshly distilled (3-aminopropyl)triethoxysilane (5). The mixture was stirred at 30 °C for 2 h, after which the solvents were immediately evaporated and the remaining powder was washed with cold ethanol, dissolved in dry THF, and reprecipitated with hexane. The product was obtained in 50% yield. Mp > 300 °C. 1H NMR (300 MHz, CDCl3, 25 °C): δ (ppm) ) 8.18-8.12 (m, 2H, H6,12); 8.098.03 (m, 2H, H1,7); 7.80 (m, 2H, H5,11); 7.46 (m, 2H, H4,10); 7.29-7.26 (m, 2H, H2,8); 4.89 (s, 2H, N-H); 4.07 (q, 3J(H,H) ) 7.95, 7.14 Hz, 12H, OCH2); 3.21-3.18 (m, 4H, N-CH2); 2.97 (t, 3J ) 7.71 Hz, 4H, Ar-CH2); 2.14 (t, 4H, CH2-CO-NH); 1.74-1.71 (m, 4H, CH2); 1.63-1.52 (m, 8H, CH2); 1.47-1.44 (m, 4H, CH2); 1.21 (t, 18H, OCH2CH3); 0.82 (m, 4H, Si-CH2). 13C NMR (75 MHz, CDCl , 25 °C): δ (ppm) ) 172.88 (CdO); 3 158.33; 156.71; 156.29 138.07; 132.93; 132.01; 129.95; 126.79; 126.24; 119.96; 119.55; 119.52; 58.44 (OCH2CH3); 33.11 (ArCH2); 31.54; 30.82; 29.38; 25.64; 25.11; 23.56; 22.89; 18.23 (OCH2CH3); 7.60 (Si-CH2). FD-MS: m/z (u e0-1) found 887.3 (100, M+), calcd 886.50. IR (KBr): 1701 (νCdO), 1644 (νCdO) cm-1. UV (CHCl3): λmax (nm) ( (M-1 cm-1)) ) 259 (34 504); 402 (12 253); 425 (25 565); 453 (31 750). Anal. Calcd for C50H74N2O8Si2: C, 67.68; H, 8.41; N, 3.16. Found: C, 66.97; H, 8.35; N, 3.25. Formulation of Sols with Chemically Attached Perylene Derivatives. For each type of sol one example is given. The concentration of the dye is calculated with respect to the ideal cured matrix (which implies complete hydrolysis and condensation of all alkoxy groups). The water for the hydrolysis reactions was added in the form of 0.1 N HCl, whereby the molar ratio between water and the alkoxy groups of the used silanes was 0.5. Methyltriethoxysilane (MTEOS)-Tetraethoxysilane (TEOS) Sol. In a 50 mL Schlenk flask, 23 mg (1.5 wt % referring to the ideal cured matrix) of one of the alkoxysilanemodified perylene derivatives (e.g., 18) was dispersed in 10 mL of dry THF. A 0.2 mL sample of 0.1 N HCl was added, and the mixture was stirred at 60 °C for 2 h under an inert atmosphere. In another 50 mL Schlenk flask, 2.6 g (0.0125

356

Chem. Mater., Vol. 12, No. 2, 2000

Schneider and Mu¨ llen

Chart 2. Perylene Derivatives for Physical Admixture to the Sol-Gel Matrix

Table 1. Perylene Derivatives for Physical Admixture and Their Corresponding Derivatives for Chemical Attachment perylene derivative for physical admixture corresponding perylene derivative for covalent attachment

32 3 and 6

33 8

34 10

35 12

36 18

37 14

38 16

39 20, 23, 25, 27, and 29

Table 2. Temperature Programs for the Different Sols 45 °C 65 °C 80 °C 100 °C

MTEOS-TEOS

MTEOS-TEOS-GPTS

TEOS-GPTS-DPSD

MPTS-Zr-GPTS

5h 4h 3h 5h

5h 4h 3h 5h

5h 5h 1h 7h

5h 4h 4h 6h

mol) of TEOS and 2.23 g (0.0125 mol) of MTEOS were stirred with 0.2 mL of 0.1 N HCl at room temperature under inert conditions until the initially two-phase mixture became a onephase mixture, the so-called “clearing-point”. At this point the alkoxysilane-modified perylene derivative which was prehydrolyzed and 10 mL of dry ethanol were added to the silanes. The reaction mixture was stirred at 60 °C for 1 day under argon, and then an additional 0.4 mL of 0.1 N HCl was added. The reaction time varied depending on the type of application, e.g., films and monoliths. For films the sol was stirred for 1 day further, for monoliths 2 days. MTEOS-TEOS-(Glycidoxypropyl)triethoxysilane (GPTS) Sol. In a 50 mL Schlenk flask, 0.272 g (0.001 15 mol) of GPTS, 27 mg (3 wt % referring to the ideal cured matrix) of an alkoxysilane-modified perylene derivative (e.g., 18), 5 mL of dry THF, 5 mL of dry ethanol, and 0.05 mL of 0.1 N HCl were stirred under reflux for 2 h. In another flask, 0.907 g (0.005 09 mol) of MTEOS and 1.3 g (0.006 24 mol) of TEOS were stirred with 0.15 mL of 0.1 N HCl at room temperature until the clearing point was reached. Then both mixtures were poured together and stirred at 60 °C for 1 day under argon. After further addition of 0.2 mL of 0.1 N HCl, the reaction mixture was again stirred for 1 day (2 days) in the case of films (monoliths). GPTS-TEOS-Diphenylsilanediol (DPSD) Sol. In a 50 mL Schlenk flask, 31.9 mg (1.5 wt %) of an alkoxysilane derivative of perylene (e.g., 18), 1.182 g (0.005 mol) of GPTS, 1.082 g (0.005 mol) of DPSD, 5 mL of dry THF, and 5 mL of dry ethanol were stirred at 60 °C until a homogeneous dispersion was reached. A 1.04 g (0.005 mol) sample of TEOS, catalyzed by 0.32 mL of 0.1 N HCl, was stirred at room temperature until the clearing point was reached. Both mixtures were poured together and stirred at 60 °C for 36 h under argon. For monolith preparation the reaction time was at least 2.5 days. GPTS-(Methacryloxypropyl)trimethoxysilane (MPTS)-Zirconium Sol. In a 50 mL Schlenk flask, 135 mg (3.5 wt %) of an alkoxysilane-modified perylene derivative (e.g., 18) was dissolved in 12 mL of dry THF. A 0.14 mL sample of 0.1 N HCl was added. The solution was stirred under reflux and inert conditions for 2 h. A 1.18 g (0.005 mol) sample of GPTS was added, and the mixture was stirred for 1 h. During this time 2.48 g (0.01 mol) of MPTS was prehydrolyzed with

0.27 mL of 0.1 N HCl in another flask until the clearing point (∼2.5 min), after which 4.679 g (0.01 mol zirconium) of zirconium n-propoxide solution (70% in propanol) was slowly added under stirring. The MPTS-zirconium n-propoxide solution was added to the prehydrolyzed perylene derivative, followed by 12 mL of dry ethanol. After the mixture was stirred at 60 °C for 2 h under an inert atmosphere, 0.36 mL of 0.1 N HCl was added. After a further 16 h (34 h) at 60 °C, the sol could be used for film (monolith) preparation. The hydrolysis and condensation rates of the alkoxysilanes, forming the network, and the alkoxysilane-modified perylene derivatives were controlled using 29Si NMR spectroscopy. Formulation of Sols with Physically Admixed Perylene Derivatives. In comparison to the former section, in this section we will describe the incorporation of perylene derivatives which are not able to react with alkoxysilanes during the sol-gel process. The same sol synthesis described in the previous section was used with the exception of prehydrolysis of these perylene derivatives, which was inapplicable. The perylene derivatives were only dissolved in THF and added to the silane precursors, forming the network. Each perylene derivative which was used for physical admixing was classed with a corresponding alkoxysilanemodified derivative as shown in Chart 2 and Table 1. Monolith Preparation. The solvent of the sol was evaporated at 15 mbar and 55 °C bath temperature until a highly viscous (honeylike) sol was obtained. The measured viscosities (viscobalance at 25 °C, 70% solution in ethanol) of the MTEOS-TEOS-(GPTS) sols were between 70 and 80 mPa s, of the DPSD sol between 60 and 70 mPa s, and of the MPTSZr-GPTS sol between 82 and 92 mPa s. It was necessary to pour the sol immediately into a Teflon vessel to avoid gelation in the flask. The bulk materials were cured using the temperature programs, which all have a heating rate of 1 K/min, given in Table 2. The GPTS-TEOS-DPSD sol builds elastic, rubberlike monoliths, whereas the monoliths of the other sols are brittle.

3. Results and Discussion Synthesis of Alkoxysilane-Modified Peryleneimides. For a chemical attachment of the perylenes to

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Scheme 1. Condensation of Perylenedicarboxylic Anhydrides with (Aminoalkyl)trialkoxysilanes

Scheme 2. Synthesized Alkoxysilane-Modified Perylenetetracarboxdiimides

the inorganic network, a suitable functionalization is necessary. We synthesized alkoxysilane-modified perylene derivatives, which were able to react with the alkoxysilanes, forming the network during the sol-gel process, by hydrolysis and condensation reactions. Starting with commercially available perylenedicarboxylic monoanhydride (4), condensation reactions with (ω-aminoalkyl)trialkoxysilanes led to the corresponding silane derivatives as shown in Scheme 1. It is known27 that methoxy groups are more reactive toward nucleophilic substitution reactions than ethoxy groups. This fact was also confirmed by the condensation reaction mentioned above. 29Si NMR spectroscopy and mass spectrometry showed that in the case of (3aminopropyl)trimethoxysilane (APTMS) (7) only the dimer of N-(3-trimethoxysilyl)propylperylene-3,4-dicarboximide (6) was obtained, whereas using (3-aminopropyl)triethoxysilane (APTES) (5), N-(3-triethoxysilyl)propylperylene-3,4-dicarboximide (3) was isolated as the monomer. Solubility studies have shown that dimers such as 6 or oligomers have a lower solubility in comparison to the corresponding monomers. Thus, it is difficult to incorporate them homogeneously in the solgel matrix and also impossible to reach a high concentration of the dyes in the host matrix. In the case of 3 we were able to incorporate 0.5 wt % in the sol-gel matrix, whereas less than 0.5 wt % 6 was incorporated. Therefore, in further experiments only ethoxysilanes were used. To improve the solubility of peryleneimide in the matrix, resulting in a higher concentration of the dye, (27) Schmidt, H.; Kaiser, A.; Rudolph, M.; Lentz, A. In Science of ceramic chemical processing; Hench, L. L., Ulrich, D. R., Eds.; John Wiley & Sons: New York, 1986; pp 87-93.

we synthesized a peryleneimide with an alkoxysilane chain on both sides of the perylene core via a condensation reaction of 3,4:9,10-perylenetetracarboxylic dianhydride (9) and APTES (5). The resulting N,N′-bis(3triethoxysilylpropyl)perylene-3,4:9,10-tetracarboxdiimide (8) however showed no significant improvement, and it was also only slightly soluble in THF (60 mg/mL). Synthesis of Alkoxysilane-Modified 3,9(10)-Substituted Perylenes. Within the scope of color tuning we were not satisfied with the incorporation of only red peryleneimides, but were looking for suitable perylenes with other absorption behavior. In addition to the well-known peryleneimides, 3,9and 3,10-substituted, the so-called peri-substituted perylenes are also described in the literature.25,28-30 We were interested in the 3,9- and 3,10-dialkylperylenes which are ω-functionalized at one or both alkyl chain ends.25 These peri-substituted perylenes absorb in the (28) Anton, U.; Go¨ltner, C.; Mu¨llen, K. Chem. Ber. 1992, 125, 23252330. (29) Pongartz, A. Monatsh. Chem. 1927, 48, 585-591. (30) Looker, J. L. J. Org. Chem. 1972, 37, 3379-3381.

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Scheme 3. Reaction of 3-Mono- or 3,9(10)-Bis(ω-hydroxyalkyl)perylene with (3-Isocyanatopropyl)triethoxysilane (IPTES) (22)

blue range of the visible spectrum. Moreover, the functional groups of these perylene derivatives allowed us to introduce alkoxysilanes and therefore to prepare yellow-colored matrixes by chemical attachment of the chromophore. Using 3-mono- or 3,9(10)-bis(ω-hydroxyalkyl)perylenes (the mixture of the isomers 3,9- and 3,10-ω-dihydroxyalkylperylene could not be separated by column chromatography or HPLC25) reactions with (3-isocyanatopropyl)trialkoxysilane (IPTES) (22) led to the corresponding silane-modified derivatives (Scheme 3). 3,9(10)-Bis(ω-carboxyalkyl)perylenes, such as perylene 30, could also be reacted with (3-isocyanatopropyl)triethoxysilane. The same product 29 was obtained if the reactive acid chloride 31 of perylene 30 was synthesized and finally reacted with aminoalkylsilanes such as APTES (5) (Scheme 4). All synthesized 3,9(10)-substituted silane derivatives of perylene have a lower solubility (between 2 and 6 mg/ mL) than the phenoxy-substituted perylenetetracarboxdiimides. However, their solubility sufficed to incorporate them homogeneously in the sol-gel process up to 3 wt %. One problem arose in the synthesis of all silanemodified perylenes. The high susceptibility of alkoxysubstituted silanes toward nucleophilic substitution, for example, by water, especially in the presence of acid or base, limited the methods of purification of alkoxysilanemodified perylenes. Usually column chromatography over silica gel or aluminum oxide was used for purifying perylenes, but the silane derivatives of these dyes could react with the column material, as is obvious from Chart 3. Separation by GPC over polystyrene columns resulted

in low yields, because most of the product remained on the columns. Therefore, the columns were also rendered useless. For that reason other methods of purification of the silane derivatives of perylene were tested. Recrystallization and/or washing processes led to purified derivatives which showed correct spectroscopic data except for some samples where the experimental values of the elemental analysis differed from the calculated ones. The values of C were decreased while the values of N were increased. This effect can be explained by physically adsorbed APTES or IPTES.34 These physically adsorbed silanes could only be detected by NMR spectroscopy if they were present in large amounts. Analytically pure samples could be obtained by GPC or extensive washing processes which both led to a drastic reduction of the yield. Therefore, not all samples for analysis were purified by these methods, due to the fact that recrystallization and/or washing processes sufficed for the application of the dyes in the sol-gel process. The physical adsorption of silanes APTES and IPTES did not have any influence on the solubility and the optical properties of the perylene. Both APTES and IPTES behaved like the network-forming silanes (e.g., MTEOS) since they could also hydrolyze and cocondense with other alkoxysilanes. Therefore, they were integrated into the network. Because the ratio of physically adsorbed silanes to matrix-forming silanes was small, the mechanical properties of the matrix were also not changed. To prevent the formation of too many side products, which could not be separated, the reaction conditions were chosen to be as mild as possible.

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Scheme 4. Synthesis of Perylene 29 by Reaction of 3,9(10)-Bis(5-carboxypentyl)perylene (30) with IPTES (22) or via the Acyl Chloride 31 with APTES (5)

Figure 1. Reaction kinetics of the MTEOS-TEOS system, catalyzed with 0.1 N HCl (two-step addition, half-equimolar water amount), controlled by 29Si NMR spectroscopy.

Chart 3. Reaction of Alkoxysilanes with the Column Material

Formulation of Sols. When sols are prepared, it is necessary to hydrolyze the alkoxysilanes which have to build up the network using water and a catalyst, for example, an acid. Besides temperature and dilution, factors determining the rate of the hydrolysis are the molarity and the molar relation of the catalyst to the alkoxy groups. Moreover, different alkoxysilanes show different reactivities toward hydrolysis. 29Si NMR experiments prove that the silane derivatives of perylene require longer hydrolysis and condensation times in comparison to the network-forming silanes such as

tetraethoxysilane (TEOS) or methyltriethoxysilane (MTEOS). This is due to the steric hindrance of the alkoxysilane-modified perylenes. Therefore, these chromophores were prehydrolyzed until some of their alkoxy groups turned into more reactive hydroxy groups which reacted with the alkoxy and hydroxy groups of the network-building silanes. The reaction conditions for the sol-gel process were chosen in such a way that a slow hydrolysis and condensation rate of the network-forming silane precursors resulted. Thus, the probability that the silane derivatives of perylene could be attached to the inorganic network was increased. For the unfunctionalized perylenes, which were only physically admixed to the sols and could not react with the network by forming a covalent bond, the same reaction conditions were chosen, except that the prehydrolyzation was inapplicable. Therefore, there was the possibility of comparison between the matrixes doped with physically admixed perylenes and the matrixes doped with chemically attached perylenes. The first system we developed was formed by TEOS and MTEOS in an equimolar ratio. These precursors which build an almost inorganic network are the best known and cheapest ones. For this system, we determined the optimal reaction conditions for incorporating the perylenes. A partial water addition (water addition in two steps, altogether to a half-equimolar stoichiometry) and an acid with low molarity were chosen. Both conditions caused a slow hydrolysis and condensation rate. In Figure 1 the kinetics of the MTEOS-TEOS sol, controlled by 29Si NMR spectroscopy, is shown. A sol which was suitable for film preparation was not reached before 48 h. After this reaction time the sol consisted mainly of T2 and T3 groups,31 that is to say, highly condensed silanes. However, hydroxy groups still existed which were responsible for good adhesion to the substrate; e.g., they were able to connect to silicon on a glass substrate surface. A comparison between sols doped with physically admixed perylenes and sols doped with the corresponding chemically incorporated perylenes showed that the latter are more homogeneous and more stable. The sols with chemically attached silane derivatives of perylene (31) T stands for three hydrolyzable groups, and Q stands for four hydrolyzable groups; The exponent gives information about the number of formed Si-O-Si linkages, i.e., the number of condensation reactions per molecule.

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Table 3. Highest Available Concentrations of the Chemically and Physically Incorporated Perylene Derivatives in the MTEOS-TEOS Sol perylene derivative cmax by chemical incorporation of perylene (wt %) corresponding perylene derivative cmax by physical incorporation of the (corresponding) perylene (wt %)

3 0.5 32 n.d.

6